Charles L. Dumoulin1, Richard P. Mallozzi2, Robert D. Darrow3, Ehud J. Schmidt4
1Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; 2ONI Medical Systems, Inc., Wilmington, MA, United States; 3General Electric Global Research, Niskayuna, NY, United States; 4Radiology, Brigham and Womens Hospital, Boston, MA, United States
An orthogonal gradient pulse is added to an MR tracking pulse sequence to change the phases of the detected MR signals. Since the phase of the signals is unknown in the absence of the orthogonal dephaser, the dephasing gradient can either increase or decrease the strength of the acquired signal. Consequently, the direction of the orthogonal gradient pulse is rotated through a cycle and the data in each cycle is processed to extract the most desired feature (e.g. maximum pixel detection). This approach increases the robustness of MR tracking in low SNR conditions.